Leaving alcohol in your flask is a sure sign of a lightweight. Any drinker worth his/her salt makes sure that their favorite flask is drunk dry each time it is used. If you absolutely have to leave some behind though, most recommendations are to make sure you don’t leave it for any more than three days.

On the rare occasion that something comes up and you have no choice but to leave alcohol in your flask, you will, of course, want to make sure it is still drinkable the next time you open it up. Knowing exactly how long you can leave alcohol in a flask will ensure that you never waste a drop.

The recommendation that you not leave alcohol in your flask for more than three days comes from retailers and users alike. This is based on the fact that alcohol will start to take on an unpleasant metallic taste if you leave it any longer in a metal flask. However, some drinkers will argue that they can easily leave alcohol in a flask for up to a month (probably those who can’t afford a refill).

What Happens to Alcohol Left in a Flask?

It is true that alcohol kills pretty much all germs, so you don’t have to worry about your alcohol going bad in the same way that food spoils. However, alcohol does tend to take on the flavors of containers in which it is stored, and really, who wants to drink something that tastes like metal or, even worse, plastic?!

Apart from taking on the taste of the container, not much else happens to your alcohol that is left in a flask. Fermentation does not continue and bacteria does not grow. Its long shelf life makes alcohol that is stored in a cool place good for a long time. It is just the strange task that stands out when it is left too long.

If you do decide to leave alcohol in your flask, there are some things to remember. If possible, remove it after a day or two, three at the latest, and transfer it to a glass container. Be sure to store a flask with alcohol in a cool dark place. This will help to slow down the development of that weird taste.

What Kind of Flask is Best for Leaving Alcohol in?

The best flask for storing alcohol is a glass flask. It does not change the taste of the alcohol the way a metal flask can. However, glass is not the most practical material for flasks. It is heavy and breakable. Therefore a good compromise is a glass flask that you can transfer your alcohol into when you come home from an outing with your trusty metal hip flask.

When it comes to leaving alcohol in metal flasks, reports vary. Some drinkers say that you can leave alcohol in a pewter or stainless steel flask for up to a month, while others say that after a day or two, you can taste the metal. It likely depends on the taste buds of the drinker and just how discriminating they really are.

Does the Type of Alcohol in my Flask change how long I can leave it there?

Flasks are made to store straight undiluted alcohol in its purest form. Therefore be sure to stick to just the hard stuff. Beer and wine are not flask friendly. Mixes are not recommended either, because they often contain carbonation, acid, or perishable ingredients that can break down the alcohol and even the flask itself. Spirits such as whiskey, rum, vodka, gin, bourbon, scotch, and certain liqueurs are the best things to put in a flask.

Alcohols to avoid putting in a flask include cream liqueurs and anything acidic such as citrus-infused spirits. These will fare the worst in your flask because cream-based liqueurs will deteriorate fastest. Acidic liquids can cause increased transfer of metallic taste to the liquor and may even cause breakdown of the metal.

Another consideration is where you will carry the flask. Any alcohol that is heated, due to body temperature or other heat source, will be more likely to take on the taste of the container. Therefore, even though a flask is often referred to as a hip flask and is even shaped to fit your hip, a better location to carry it is in your outside jacket pocket as it will not be as warm as next to your body.

The serious drinker will make sure to use his flask daily to avoid this storage problem. Regular drinking followed by rinsing your trusty flask and letting it air dry is the hands-down, best way to ensure that no good alcohol goes to waste. So, before storing your flask, take a final good healthy swig and drain it and you’ll never have to worry about funny-tasting booze again.